N° 51. — Conductivité ionique du protoxyde de cuivre en fonction de sa composition vers 400 °C

Nous avons déterminé la partie ionique de la conductivité électrique du protoxyde de cuivre en fonction de la température entre 336 et 456 °C et de la composition entre les deux limites d’existence de l’oxyde vers le cuivre d’une part et l’oxyde cuivrique d’autre part.Cette détermination a été effectuée par analyse des caractéristiques courant-tension d’une cellule constituée par la chaîne de conducteurs : cuivre anode, protoxyde de cuivre, bromure cuivreux, cuivre cathode.Le nombre de transport ionique est de quelques dix-millièmes. La conductivité ionique varie comme la puissance — 0,92 environ de l’activité du cuivre dans l’oxyde, soit comme la puissance 0,23 de la pression d’oxygène en équilibre avec l’oxyde; ces valeurs montrent que les lacunes d’ions cuivreux et les lacunes électroniques du modèle de WAGNER doivent être très fortement associées

Les obstructions à l'écoulement urinaire (méthode de mesure de la résistance, modélisation de la mécanique prostatique, particularités d'écoulement dans l'urètre)

Les méthodes de mesure de la résistance urinaire ne permettent pas d'affirmer sûrement l'obstruction, en raison de fondements physiques et physiologiques non vérifiés. La comparaison de mictions liquides et gazeuses montre la variabilité du diamètre urétral. Une méthode de mesure fondée sur la physique et la physiologie est proposée. Un appareillage permettant de mesurer la vitesse du jet et la pression vésicale par une méthode externe est décrit. La mécanique prostatique normale et de modèles d'HB? est modélisée par éléments finis. l'ouverture urétrale est mesurée en fonction de la nature des nodules et de la géométrie. Il n'y a pas de corrélation entre volume prostatique et gêne urinaire. Enfin, les obstruction sont examinées selon leur nature et leur localisation. Les moyens physiques de diagnostic sont examinés et les méthodes thérapeutiques jugées selon des critères mécaniques. L'obstruction liée aux valves urétrales et la mécanique du reflux intravésical sont expliquésCurrent methods of urinary flow resistance meausrement are inadequate because of dubious physiological and physicaf fondations. The companson of fiquid and gas micturnions proves the variability of the urethral opening. A resistance measurement method based on physics and physiology is proposed. A detailed description of the principles of an equipment allowing to measure urinary jet speed and bladder pressure by a minimally invasive method is proposed. The mechanics of normal prostate and of BPH is model/ised by finite elements method. The urethral opening is measured according to the nodules composition and the geometry. There is no correlation between prostate volume and urinary discomfort. Obstruction causes are examined according to their nature and location. Physical methods allowing the diagnosis are examined. Avai}abJe therapeutic methods are judged accordinf to mechanical criteria. The obstruction associated to posterior urethra vlaves and the mechanics of intravesical reflux are explained.NANCY/VANDOEUVRE-INPL (545472102) / SudocSudocFranceF

Kinetic modeling of the transport of dust particles in a rarefied atmosphere

International audienceWe propose kinetic models to describe dust particles in a rarefied atmosphere in order to model the beginning of a Loss of Vacuum Accident (LOVA) in the framework of safety studies in the International Thermonuclear Experimental Reactor (ITER). After having studied characteristic time and length scales at the beginning of a LOVA in ITER and underlined that these characteristic scales justify a kinetic approach, we firstly propose a kinetic model by supposing that the collisions between dust particles and gas molecules are inelastic and are given by a diffuse reflexion mechanism on the surface of dust particles. This collision mechanism allows us to take into account the macroscopic character of dust particles compared to gas molecules. This leads to establish new Boltzmann type kinetic operators that are non-classical. Then, by noting that the mass of a dust particle is huge compared to the mass of a gas molecule, we perform an asymptotic expansion to one of the dust–molecule kinetic operators with respect to the ratio of mass between a gas molecule and a dust particle. This allows us to obtain a dust–molecule kinetic operator of Vlasov type whose any numerical discretization is less expensive than any numerical discretization of the original Boltzmann type operator. At last, we perform numerical simulations with Monte–Carlo and Particle-In-Cell (PIC) methods which validate and justify the derivation of the Vlasov operator. Moreover, examples of 3D numerical simulations of a LOVA in ITER using these kinetic models are presented

Probabilistic aspects of finance

In the past decades, advanced probabilistic methods have had significant impact on the field of finance, both in academia and in the financial industry. Conversely, financial questions have stimulated new research directions in probability. In this survey paper, we review some of these developments and point to some areas that might deserve further investigation. We start by reviewing the basics of arbitrage pricing theory, with special emphasis on incomplete markets and on the different roles played by the "real-world" probability measure and its equivalent martingale measures. We then focus on the issue of model ambiguity, also called Knightian uncertainty. We present two case studies in which it is possible to deal with Knightian uncertainty in mathematical terms. The first case study concerns the hedging of derivatives, such as variance swaps, in a strictly pathwise sense. The second one deals with capital requirements and preferences specified by convex and coherent risk measures. In the final two sections we discuss mathematical issues arising from the dramatic increase of algorithmic trading in modern financial markets.Comment: Published in at http://dx.doi.org/10.3150/12-BEJSP05 the Bernoulli (http://isi.cbs.nl/bernoulli/) by the International Statistical Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm